Drug-coated medical balloons are used to deliver a therapeutic agent to a location inside the body, such as to a site within a blood vessel. Medical balloons are used in a wide variety of minimally-invasive or percutaneous medical procedures. Medical balloons having drug coatings may be used to treat diseased portions of blood vessels. Typically, the balloon is inserted through a peripheral blood vessel and then guided via a catheter through the vascular system to the target intravascular site.
The balloon typically is folded to make it more compact and thus facilitate transport to its destination. Once appropriately positioned at its destination, the balloon is inflated, causing it to unfold and press against the surrounding tissue, resulting in release of the drug to the surrounding tissue. There can be substantial loss of drug both during transport of the balloon, to surrounding fluid, during removal of a protective sheath surrounding the balloon, and during unfolding. During removal of a sliding protective sheath, friction between the sheath and therapeutic agent on the balloon surface that is in contact with the sheath can dislodge and cause loss of the therapeutic agent. Also, in the folded state, drug-coated balloon surfaces may be pressed together, causing the drug layer on one surface to come into contact with the drug layer on the opposing surface. When such layers are separated from each other during inflation, the drug layer from one surface can stick to the drug layer on the other surface, resulting in loss of drug into surrounding body fluid and uneven delivery of drug to tissue. Thus the quantity of drug that reaches the intended tissue can be difficult to measure or predict and the application of drug to tissue is non-uniform.
Drug-coated medical balloons and other medical devices are often used with retractable sheaths to deliver the medical device to a location inside the body, such as to a site within a blood vessel. The medical device can be a stent delivered via a stent delivery and dilation catheter system. The stent delivery catheter can employ a retractable sheath such as a rolling retractable sheath that is retracted to release a medical device such as a self-expanding or balloon expandable stent. Sheath removal also can cause drug loss from the surface of the sheathed medical device.
The present invention addresses these needs and deficiencies in its various embodiments as described below.